Monday, November 22, 2010

King County Metro, Snow, and Real-Time Tracking

You'll notice that there is currently no real-time data available or King County Metro buses in OneBusAway. The issue is that King County Metro pulled the real-time feed because of the snow and adverse weather reroutes today. Why would they pull the real-time feed in conditions where you'd probably agree that it would be extra useful? They do so because the current tracking system for King County Metro buses doesn't work well when buses are on adverse weather reroute.

When a bus is on adverse weather reroute (see http://metro.kingcounty.gov/up/rr/adverseweather.html for a current list), real-time arrival predictions are not accurate for that route. Why is that?

The position of each bus in Metro KC is not tracked with GPS, but rather with a decidedly lower-tech approach. Each bus is outfitted with a device that can radio the current odometer reading for the bus back to a server. If we know the odometer reading when the bus starts its route, we can periodically monitor the real-time odometer readings to determine how far along the route the bus has traveled. This gives us an estimate of position and from there, an estimate of how early or late a bus is. This is how http://mybus.org works and OneBusAway is just a fancy front-end to MyBus.

The problem comes with buses on adverse weather reroute, or any type of temporary reroute. When a bus goes on reroute, the physical route changes and the odometry calculation based on the original route used above is no longer accurate. In a perfect world, we would know when a bus is on reroute and adjust to its new route. Unfortunately, there is currently no automated way for handling this situation.

The result, unfortunately, is that on days when it is often cold and miserable and you'd rather not wait outside any longer than you have to for your bus, the real-time tracker often doesn't work. Ironic, huh?

I'd argue that King County Metro went too far in cutting the ENTIRE feed, as there are plenty of buses that aren't on reroute where the real-time tracking would be extra useful to riders today. If you feel the same way, definitely let them know.

17 comments:

Jim said...

Interesting. I've heard rumors that KCMetro is in the process of switching to GPS. Do you know if that's true at all?

Brian Ferris said...

@Jim it's true, but still ~ 2 years away

DarkHawke said...

Wow. I knew that Metro wasn't using GPS, but odometer readings? Thankfully I missed whatever trials occurred today, but in the past WHEN THE CITY PLOWED AND SANDED/SALTED THE STREETS, Metro service was good enough that while there were longer than normal waits, the system was still usable during snowy/icy conditions. Hope they're up to snuff for the next two days! ;)

Sam L said...

What is the best way to give Metro feedback (on not pulling the feed entirely)?

marc said...

Of course something is better than nothing...

Laura said...

i need info on the 5.
i think it is basically running smoothly. - one small re-route. i wish i could see the info!

Fisher said...

WOW! This blows my mind. It makes no sense to take the live tracking off of all the routes though. Certain snow routes don't deviate much from a normal route, i.e. my route the 120. It only really changes at the end of the route going into Seattle AFTER it's made all the regular stops.

M Newell said...

I provided feedback to the Tracker team yesterday via the KCM website. Below is their reply. Either Tracker isn't the same as KCM or Dean doesn't understand that if KCM stops the feed, all the alternates he suggests are dead as well.
----
Thank you for contacting King County Metro Transit about Tracker. During this period you may wish to go to www.onebusaway.org, mybus.org or busview.org for your Tracker needs.

Sincerely,

Dean Bryant

On behalf of Tracker
-----

Brian Ferris said...

@M Newell: HA! That just made my day.

Shannon said...

King county, on the cutting edge as usual.

Crystal said...

wow! good to know. all this time i thought the bus and/or stops had sensors/gps....

konradm said...

On the old iphone/mobile-interface someone wrote "You're bus may be rerouted or cancelled." -- should be "Your bus may be rerouted or cancelled."

eric1972sea said...

I never knew that Metro did not use GPS that explains how they do it in the tunnel.

Joseph W. said...

I'm confused. Do any re-routes add more than 5% of extra distance to a route ? It seems to me that leaving the trackers on could have made the timings a little erratic (particularly with slipping wheels throwing off the odometer) but probably not unusable. Are you sure this isn't like an airline pushing off from the gate on time only to wait on the tarmac being called "on time" in the records ?

OffBeatMammal said...

2 years for GPS?! surely a local Telco (T-Mo) could donate some old handsets and an EDGE data plan and have the buses phone in their location every couple of minutes? Heck, drivers could even run an app that they enter their route and turn on the app (hmm, opportunity for Windows Phone 7 perhaps?) and it pushes data back to base, and when they get home they hit "stop" on the app (heck, with geolocation it could even stop/start automatically when they are at start/end of a route). Data could be compared to the odometer and both published...

LeoFire said...

The system can't handle the math when it sees the rte 5 bus where the rte 3 bus should be. So it screws up the calculations and then you'd be mad because the system said the bus should be here in 3 minutes, but it was actually an hour. So, do you want wrong information or none. I'd rather have none. it was easy to tell that the buses would be late becuase of all the sliding vehicles right in front of your face. Also, complain about 2 years for GPS all you want, but if you don't want to find a funding source for them, you have no right to complain about it. They do an amazing job with the small fares they charge and with the amount of budgetary cut backs they've had in part due to the fact that seattle wont pass a tax raise. Quit complaining and find out how you can help.

oib1 said...

Boy, that odometer system must work great when drivers go search for donuts or a rest break.

Has anyone been to DC, San Francisco, Toronto or Boston where they use the Nextbus system - why is Seattle in the dark ages??